Spatiotemporal trends of area burnt in the Iberian Peninsula, 1975–2013

In Portugal and Spain, fire regimes have been significantly altered due to changes in anthropogenic and climatic factors. The development of a fire management strategy should take into account the past trends of fire incidence. We analyse the spatial and temporal trends of burned area in the Iberian Peninsula, merging four decades of forest fire data from the two countries. Theil-Sen slope and a spatial version of Mann-Kendall test are used to test the significance of trends. Excluding some small cases, all significant clusters in Spain correspond to regions of decreasing trends of burnt area. Portugal exhibits contrasting trends, with a large cluster of increasing trend of burnt area in the northwestern part of the country and a large cluster of decreasing trend in central Portugal. A regression analysis performed between the burnt area and the Daily Severity Rating (DSR), a measure of fire suppression difficulty, for the largest significant clusters reveals that climatic factors explain only in part the burnt area trends. Anthropogenic factors also play an important role. In northwestern Spain, fire suppression has contributed to a decreasing trend of burnt area even if the area of forest and the population has increased in the last decades. In central Portugal, the decreasing trend in burnt area is mostly related to the population decrease and the rural abandonment. Regarding northwestern Portugal, it is a region where agriculture is the dominant land cover type and the urban area doubled since 1990. This is indicative of an extending urban-rural interface, which contributes to an increase in fire incidence.